630 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



straight. From its anterior inner part a plate of hone folds back to 

 support the hypo and hypercoracoid. 



The latter is a thin plate, not strongh" ossified. Through it and 

 entirely within its edges is a very large fenestre, which from the outer 

 side seems to be partly inclosed by the clavicle, as the hypercoracoid 

 is attached fiat against the inner surface of that bone. 



The hypocoracoid is attached along its entire anterior edge to the 

 clavicle without leaving the usual opening between. The lower edge 

 is thickened and extends backward as a long process, which, growing 

 thin posteriori}', is divided for most of its length into many bristle-like 

 filaments. 



The three lower actinosts are long and rod-like, with large spaces 

 between them. The second and third are somewhat closer together 

 than the others. The fourth is smaller, and is articulated closely 

 against the upper outer end of the hj-percoracoid. Two of them are 

 above the hypercoracoid and two above the hypocoracoid. 



The postclavicle is a broad triangular-shaped bone, with a process 

 running obliquely from the upper corner for articulation with the 

 clavicle, and the posterior corner prolonged into a long ray of bone. 



The Shoulder Girdle of Fistularia petimba. 

 fistulariid^. 



The post-temporal is united to the cranium bv dentate suture, form- 

 ing an outer produced angle on each side wholly posterior to the 

 pterotic. It is articulated laterally to the epiotic and the exoccipital, 

 posteriorly slightl}' to the frontal and broadly to the pterotic. 



V ^T* *'* 



Fig. 4.— Right shoulder girdle op Fistularia petimba from outside, o, actinosts; cl, 

 clavicle; kyoc, hypocoracoid, hupc, hypercoracoid, p, pectoral fin; pel, postclavicle, and 



Scl, SUPERCLAVICLE. 



Though the post- temporals appear to play an important part in 

 forming the cranium when viewed from above, they form no part of 

 the cranial wall, being only thin sheets of bone attached at their lat- 

 eral and anterior edges. Were they removed the remaining elements 

 would ))ear about the same relationship to each other as the}^ do in 

 the cranium of Aulostomus. 



